This paper is concerned with the role of speech in the development of control of cognitive processes, with particular attention paid to the nature of bilingualism. It is stated that exposure to a second language provides a way of overcoming the encapsulation of the mind that develops when an individual is exposed to only one language. In order to understand the phenomenon of bilingualism, it is necessary to adopt a historical perspective and to note what has changed and developed in the lifetime of both a group and an individual. There is a need to explain how it is that two languages interact so that a new kind of consciousness is the outcome. In considering bilingualism, three central questions are: (1) What is consciousness? (2) How did it come about? (3) What are the particular understandings of a given cultural group and what is that individual's experience within that cultural group? These questions are discussed in light of Bain's work on the nature of human consciousness. (CLK)